* {
    padding: 0;
    margin: 0;
}
ul {
    list-style: none;
}
// & 表示上一级选择
.box {
    width: 1400px;
    height: 800px;
    margin: 0 auto;
    border: solid;
    &-header {
        height: 100px;
        background-color: red;
    }

    &-main {
        height: 650px;
        display: flex;
        &-left {
            flex: 1;
            height: 650px;
            background-color: pink;
            ul {
                li {
                    &:hover {
                        color: green;
    
                    }
                    &:active {
                        color: orange;
                    }
                }
              
            }

        }
        &-right {
            flex: 2;
            height: 650px;
        }
    }

    &-footer {
        height: 50px;
        background-color: orange;
    }

}